The TX9S is a large format, high output subwoofer with a full frequency response (down to 30Hz) and longer excursion voice coils. The dual 18" front loaded TX9S handles bundles of power and is perfect for those who are looking for lots of low, low bass. The cost effective TX9S incorporates rear mounted wheels for ease of transportation. The frequency response of the TX9S makes it appropriate for use with all boxes in the TX line including the TX4 and TX8. The TX9S is especially well suited as a music playback subwoofer.